Phenol and cyclohexanone are important materials in the chemical industry and are useful in, for example, the production of phenolic resins, bisphenol A, ε-caprolactam, adipic acid, and plasticizers.
Currently, a common route for the production of phenol is the Hock process. This is a three-step process in which the first step involves alkylation of benzene with propylene to produce cumene, followed by oxidation of cumene to the corresponding hydroperoxide, and then cleavage of the hydroperoxide to produce equimolar amounts of phenol and acetone. However, the world demand for phenol is growing more rapidly than that for acetone. In addition, the cost of propylene feed is generally high.
Thus, a process that uses alternative feeds and coproduces higher-value ketones, such as cyclohexanone, rather than acetone may be an attractive alternative route to the production of phenols.
It is known from, e.g., U.S. Pat. No. 6,037,513 that cyclohexylbenzene can be produced by contacting benzene with hydrogen in the presence of a bifunctional catalyst comprising a molecular sieve of the MCM-22 type and at least one hydrogenation metal selected from Pd, Ru, Ni, Co, and mixtures thereof. This reference also discloses that the resultant cyclohexylbenzene can be oxidized to the corresponding hydroperoxide which is then decomposed to the desired phenol and cyclohexanone co-product.
In the hydroalkylation step, both the conversion of the aromatic compound (e.g., benzene) and the selectivity of the target alkylated aromatic compound are substantially determined by the performance of the hydroalkylation catalyst. It has been found that the activation process of the hydroalkylation catalyst in the presence of hydrogen can affect catalyst performance significantly. Although various activation processes for the hydroalkylation catalyst have been explored and disclosed before, there is still room for improvement in this regard.